Nannydaft If he is making a working visit, then he must be making it to another person working in the same field, who he wants to talk to directly. The visit is either essential for both or inessential to both.
Inessential travel into Scotland is now seriously discouraged.
Nicola Sturgeon will no doubt think his trip is not needed - there are telephones, zoom meetings, emails, tweets and in the last resort even letters.
I would say there are two reasons for his visit - to try to assert his superior power as pm of the UK over the First Minister about the devolved issue of Health Matters, or to get in a little break for himself. Maybe he'll bring a tent and a primus stove.